


All You Need

by wowthisissad



Series: Incest [8]
Category: Haikyuu!!
Genre: Crying, Cuddling, Dry Humping, Dubious Consent to Enthusiastic Consent, F/M, Fingering, Groping, Guilt, Incest, Non-Penetrative Sex, Sibling Incest, Somnophilia
Language: English
Status: Completed
Published: 2020-12-06
Updated: 2020-12-06
Packaged: 2021-03-09 18:22:04
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,336
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27920707
Author URL: https://archiveofourown.org/users/wowthisissad/pseuds/wowthisissad
Summary: You and your big brother Issei had grown apart when he entered highschool. But, when you followed in his footsteps, after years of not really interacting with each other, you became best friends all over again.But, with lack of contact for so long, both of you had lost your gauge for what was truly appropriate between siblings.
Relationships: Issei Matsukawa/Reader
Series: Incest [8]
Series URL: https://archiveofourown.org/series/2027141
Comments: 12
Kudos: 117





	All You Need

**Author's Note:**

> To those who may have inquiries about my tumblr, I have been stressed for a long time and while I tried to keep it together, it’s gotten to me. My tumblr, which was once @wowthisissad, has since been deactivated. I’m not going to elaborate, but I can assure you that I will be keeping my ao3 up, and will still be posting fanfictions. You may still comment and request things here in my ao3 comments, and I will miss the interaction I got back on tumblr, but for the sake of my mental health, this is the best decision I have made for a while.

He had always been doting. Ever since you could walk, he was right behind you with a pack of bandaids in case you fell. In the photo album from when you were a baby, there were a minimum of 35 pictures with both you and Issei- quite a few of them with him pressing a dainty kiss to your baby head or entertaining you with a toy in front of your face. 

When you started eating by yourself, he had a careful eye trained on you if you choked. While your parents knew he meant well, his aggressive slapping to your back when you gagged on a piece of food wasn’t as helpful as he intended it to be.

When you started attending primary school with him, he’d walk you to and from your classroom, scrutinizing the room for potential bullies. He’d make sure to hang out with you whenever he could- on the playground, in the cafeteria, and when he held your hand on the way to the car-rider line.

In middle school, he’d stay up later than he needed to help you out with confusing homework, and multiple times he’d wake up to you knocking at his bedroom door with tears in your eyes, blubbering about some drama that was occurring between you and your friends. He’d lift up the blankets to his bed and let you crawl in, pressing your head to his chest while you cried, and he’d lay there petting your hair, making small noises to let you know that he was still listening.

But, when he entered highschool, that’s when your relationship with each other began to change. He had practice almost every morning and night- suddenly he didn’t have the energy to help you with homework or cuddle you when your friend was being a jerk. You drifted away from each other without even completely realizing it. You sobbed into your pillow and struggled through equations while he worked out at the gym or re-evaluated his dietary plan for volleyball. 

You talked to each other less and less until you stopped talking at all. Both of you made a habit out of holing up in your rooms, ignoring each other unless you were forced to interact. Late night kitchen endeavors became a meeting ground where nothing but silence stretched between the two of you as you filled your cups with lukewarm water and sipped on them while avoiding eye contact.

And honestly, it wasn’t painful. It became your normal. You didn’t even entirely think of him as “issei-nii” anymore- not that it was a bad thing to drop the honorific, but it was an obvious sign as to what the two of you thought of each other: nothing.

Then, for some reason, when you finally entered highschool, everything zoomed back to when you were young again.

Maybe it was because you were forced to wake up when he did as he had become your ride to school- even though he had volleyball. Maybe it was when he would lend you his jacket as a pillow if you wanted to sleep in the bleachers during his morning practices. Maybe it was because his route to his class passed yours, so now you were walking together every day. Maybe it was when he introduced you to his teammates Oikawa teased you about how much “your nii-san talks about you a lot, you know~” and Issei’s face flushed and he shoved Oikawa playfully.

Maybe it was then that everything clicked back into place.

“Issei,” had become “Issei-nii,” and silent night adventures transformed into quiet laughter as you tried to hold in your giggles, everything funny for no reason at all. In the car rides, instead of keeping your bag between the two of you, you tossed it in the backseat and chatted with him the entire time, play-fighting over what radio station to listen to. Your whimpers into your pillow changed into soft knocks to his door and him slowly swinging it open, allowing you in with a tired grumble of “you’re getting too big for this,

imouto,” as he tugged you onto his bed, letting you koala around him to leech off of his body heat.

Your parents were ecstatic at the two of you finally getting along again- happy to see real, genuine interactions beyond the occasional family photo with a forced smile and tense stances.

Not only did you become emotionally comfortable with him again, you became more physically comfortable. Casual touches were normalized between the two of you- head pats, cuddles, shoulder and back rubs- all was a-okay. Plus it didn’t hurt that your sleep schedules changed a bit to coincide with one another’s: you getting used to waking up early and him adjusting to staying up late. Night after night you’d sit in his or your room, talking about anything and everything, legs intertwined as you got as close to him as you could, denying the blanket that he offered when you complained about how it was cold.

After all, you only needed Issei-nii.

But, after not having been around each other for so long, it became hard to discern what was truly _casual._ When you curled up in his bed, when his hips pressed against yours and his hands brushed your chest, you couldn’t find it within you to try and stop him- especially if he was asleep. Also, you had the tiniest bit of confusion when it came to wearing different things around him. You had developed a preference for tank-tops and cotton shorts over long sweatpants and t-shirts when sleeping at night, and your fore-going of a bra was also something that had to be taken into consideration. 

Issei brought it up one time when the two of you were entangled under the blankets, your barely covered tits pressed up against his chest as you looked up at him.

“Why wouldn’t I wear this when I’m around you? It’s comfortable, and it’s not like you’re a creep or anything.”

It’s pretty fair reasoning, in all honesty. But still, seeing you like that all the time- it was weird. It made him feel things he _knew_ he shouldn’t be, yet… Yet he couldn’t stop.

I mean, can you really blame him? Issei has seen you grow from a gangly little kid to- to _this_ \- and here you are pressing up against him and calling him your nii-chan and him addressing you as Imouto even though both of you are far too old to be using such silly names anymore. His heart beats out of his chest when he sees you pull your knees up to your chest on car rides, your skirt sliding down to show the very hem of those pretty pink panties. His hands get sweaty and he fumbles the ball when he watches you take a nap during his morning practices, your chest rising and falling with every breath- more than once he’s been hit right in the face because he was too busy staring at you. 

He wants to think he just cares about you a lot- maybe a little bit more than he should, but Issei knows that’s not the truth. He knows his stomach doesn’t flutter because he’s ill, he knows his face doesn’t get flushed because he’s hot, and he knows him fisting his cock every night while he looks at pictures of you isn’t just a phase that’ll eventually pass.

He’s cried over it, he’s screamed into his pillows, and he’s cum in his pants because _Issei Matsukwa is a_ **_sister-fucker_ ** _._

But he’s not stupid, and he’s not cruel. You’re not meaning to tease him the way you do- you can’t help that you’re as pretty as you are. After all, you two share the same genes.

The sheer idea has made him gag at himself, dry heaving over the toilet while the corny video still played on his phone- _“Step-brother fucks bimbo sister stupid!!”_ He _hates_ the way he thinks. He hates that his brain has changed to work the way that it does, he hates that he can’t tear his eyes away from you and he _especially_ hates that you seem to be well aware and aren’t doing anything to stop him.

He sees the way your eyes flicker to him when you wear revealing clothing, he catches how you pull your skirt up an inch or two higher up than it needs to be when he walks you to class. He’s accidentally walked in on you showering before (you really need to start locking the door), and you didn’t even make a move to cover yourself- you just asked what he was doing while he ogled at your tits before snapping out of it and running off.

But, obviously, Issei can’t really make assumptions- not in a situation like this. So he pushes through, accepting your cuddles and soft touches, lending you his jackets and averting his eyes when you wear lower-cut shirts. He never intended to make any sort of move, he figured he’d just let it happen, holding himself on the shortest leach possible until the both of you moved out and found your own ways in life. Then he’d find a girl who looked a lot like you, date her, maybe marry her, and forget all about his affections towards you.

He had it all planned out-

So how the hell did he get here?

Issei wasn’t really prone to wet dreams. He was generally regular with how he jerked off, but every blue moon he’d wake up with a wet stomach or a raging hard on.

And he just woke up with a boner.

Usually this would be fine, he’d finish himself off and then go back to bed, but he can't because _you’re in the same bed as him_. He’s desperately trying to keep his breathing patterns even as to not wake you up while he tries to control himself- which is quite the hard endeavor when his dick is nestled in the curve of your ass. You had decided you felt like spooning tonight, Issei’s arms wrapped around your waist and his chest up against your back, and now his dick pressed against your butt.

He internally curses at himself, knowing he couldn’t move away from you without waking you up. But, before he can make any executive decisions, you sigh softly and move your body closer to his, accidentally rubbing against his covered cock. Issei hissed quietly through his teeth, slamming his eyes shut as he refrained from thrusting his hips up.

“Fuck-“ he whispered, slouching over at a borderline painful angle in a fruitless attempt at removing the stimulation your body offered to him. His face grew panicked as you followed him, making an upset grumbly noise as you shifted to follow his body heat. He sucked in a tight breath, frustrated tears building up in his eyes and blurring his sight.

He’s done so well for so long- is this really going to be his breaking point? A wet dream and a boner during a cuddle session?

Issei’s eyes flickered over to the clock on his nightstand, the black screen flickering “1:36 am” in a blocky red font. He internally groaned, knowing he had to get up for school in 5 hours. His eyes dragged back down to your sleeping form, and the guilt he had harbored for so long came crashing down all over again. He sucked in his bottom lip as you shifted, unintentionally grinding up against him. A tear slipped out of his eye and onto the pillow without a sound, and he silently prayed to any and all God’s that you would forgive him if you woke up.

He just- he just _can’t hold back anymore._

At that, Issei began the regretful roll of his hips, slowly pressing himself against your plump body. Shivers ran up his spine as he finally got what he wanted, and his hands lightly squeezed at where they sat at your waist. He felt his heart clench in his chest as the bed squeaked quietly with every small move, and another salty tear fell from his eye.

“Shit- I’m sorry imouto- your nii-chan is so _sorry- fuck-“_

He couldn’t stop himself from pulling you as close as he could, tossing his leg over yours as he continued his thrusts. His hand that was on your waist slid up to hesitate over your barely covered breast- the tank top you’re wearing barely hides anything. Issei’s finger barely grazed your chest, and he could feel his face flush a bright red when he realized your nipple was hard. He could very well blame it on the fan next to his bed that consistently blew cold air at him, but the thought of _“she’s enjoying this~”_ floated through his brain.

At that, he gave in, cupping your tit in his hand, a shuddered and breathy moan slipping out from his mouth. He carefully pulled your top down, getting a grasp at your uncovered tit. He burrowed his face in your shoulder, eyes slipping shut as his other hand made quick work of pulling his boxers down and grinding his cock between your covered ass cheeks. He whimpered into your skin, pressing wet kiss after kiss to any skin available, whispering apologies under his breath as he went.

Issei felt the familiar coil in his gut- his whimper switching to soft, open mouthed gasps. He felt close, the tip of his cock catching on your panty-covered asshole every few thrusts, the idea of properly fucking you making his brain run wild. He was gonna cum, and he whispered that into your ear, a depraved and guilty satisfaction unfurling in his chest.

“I’m gonna _cum_ , imouto- it’s gonna get all over your back and ass- I’m sorry, baby- I’m so fuckin sorry- _shit-_ it’ll never happen again, I promise, just stay asleep for a _little while longer_ , okay? Be a good girl and stay asleep for your _big brother_ \- it’ll all be over soon.”

But then, right as Issei was on the edge of orgasm, your quiet, sleepy voice drifted out from your mouth. 

“Iss- Issei-nii?”

_Oh shit._

_Oh_ **_fuck._ **

He completely froze, eyes wide as you yawned and stretched your arms and legs out like a cat after a nap. He had half a mind to pull his hand away from your chest, but you trapped him, pressing your arms down to your side. Panic enveloped him and he tugged at it, forgetting about his hard-on. You wriggled around, turning to face him with a grumpy look on your cute, tired face.

“Why’re you touchin’ me, nii-chan?”

Shame and anxiety sat heavy in his gut, and he tugged at his hand weakly, the tears full force now. He ignored your question, hoarsely asking you to let him go.

“Please- please just go back to bed- I’ll turn around I’m- I’m sorry-“

You huffed and grabbed his hand, pulling him closer and reattaching it to your chest. Issei sputtered, his cock throbbing at your stubborn actions.

“If you wanted this, you could’ve just asked, dummy.”

“I- what- wait hold on-“

You turned to look at him again, rolling your eyes at him like he was stupid.

“Did you forget that I’m a light sleeper? I’ve been letting all of this happen, and I’m _wet_ , Issei-nii. Are you gonna take care of it or am I gonna have to all by myself?”

Issei was stunned, his face a bright red as he processed the information.

“You- you want me too?”

You snorted at him, a teasing grin sliding onto your expression.

“ _Yes,_ Issei, I want you too. Now finger me or I’m gonna go to my room and never talk to you again.”

He balked at the bluntness before getting the hint and rushing to bring his hand down to your abdomen, hesitating above the hem, his eyes flickering over to you, silently asking for approval. You nodded, and he slid his hand underneath, sucking in a tight breath.

You’re _soaked._

His thumb brushed over your clit, and his shuddered sigh slipped out along with your soft whimper. He travelled farther, middle finger tracing over your labia in a v-formation before pulling his hand out to stare in awe at the strings of slick between his fingers. You moved to tap his cheek, sitting up the slightest bit to catch him in a kiss when he turned to face you, muffling his soft moan. You detached for a moment, smirking at the lustful haze over his eyes.

“I bet you can finger me and grind against me at the same time, right, Issei-nii? Why don’t you cum all over your baby sister?”

“Fuck- imouto-“

You shushed him, knowing he was overwhelmed. After all-

You’ve been watching him pine over you for months now.

“Go ahead, nii-chan. Do what you want, do what you gotta do.”

He hesitates again for a half second before grinding his hips against your ass, a soft moan tumbling from his lips. His thumb begins a circular movement around your clit while his middle finger prods at your hole, dipping the tip in and out. You’re unable to hold in your gasp when he slides his long finger inside, thrusting in and out. The sound you make is loud- _too_ loud- and Issei quickly silenced you by pulling you into a sloppy kiss, his tongue intertwining with yours, your saliva mixing together.

You made a choked noise when he pushed a second finger inside to the knuckle without warning, and he snickered into the kiss when you lightly elbowed him. 

He murmured “be quiet, imouto,” as he kissed down your neck, sucking gently at your pulse point, making sure not to leave a mark. As Issei gained confidence, his quick and stuttered humps turned into slow grinds, dragging his weeping cock between your ass cheeks, precum dripping onto your panties. His fingering became rougher, slick sounds filling the room as he angled his hand to graze your g-spot, a smirk on his lips when you tossed your head back and groaned into the pillows.

The change from meek and guilty to strong and regretless was fast, and something that got you wetter than nothing else.

Issei’s orgasm had already been ridiculously close, but now with the added stimulation of you pushing back onto him, _plus_ knowing that you returned his feelings, the coil was near snappy already. 

“I-imouto- I’m already gonna _cum~_ It’s gonna make a _mess_ \- can you cum too? I wanna feel you cum on my fingers- I want it _so bad_ , Y/N, I _want it_ -“

You whimpered, the heat in your stomach near boiling. 

“Please- just touch me a- a _little bit more-!!_ ”

He angled his fingers harshly, pressing directly onto that sweet, spongy spot as he teased the underside of your clit, and you clenched, eyes tearing up as your orgasm crashed over you. At the same time, Issei used his other hand to pull you flush with him as he came, his eyes squeezing shut as he borrowed his face into your shoulder, trembling as his semen shot out in spurts. Both of your breathing patterns were shuddered as you came down from your respective highs, and as he dazedly pulled his hand out of your underwear, he snorted softly when he noticed his fingers had pruned up the slightest bit. 

As you caught your breath, your eyes drifted over to the clock on his nightstand.

2:07 am.

“Issei-“ you started, but trailed off, not knowing what to say.

“Just- just go t’sleep. We can talk about it in the morning.”

He brushed you off as he tucked himself back in his boxers and cuddled up to you, pressing a lazy kiss to your shoulder. You couldn’t help but let a smile slide onto your face, relaxing into the mattress.

You definitely _weren’t_ going to talk about it, but that’s okay.

As long as you have Issei-nii, all is well.

**Author's Note:**

> Don’t hesitate to leave a comment! If you’ve read any of my other fics and seen the comment sections, then you know I try to respond to every one I get! All thoughts and ideas are welcome - and if you happen to have a particularly inspirational idea, I may just make a fic based off of it! So, go ahead! :)


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